swansont

There's a huge difference between intelligence and experience. Hang n there.

How did you figure the total energy out? And how does that affect the range of the EM or gravitational force? And what does SM represent?

The term is c2t2

Light is not charged. Magnetism affects moving charges.

Energy is the capacity to do work. It's not particulate, though it can be quantized.

Magnets don't have a gravitational field, they have a magnetic field. The EM exchange particle is the photon.

yes, a photon of sufficient energy can create an electron/positron piar. But that's very different than an electron and a photon are interchangeable. When they annihilate they produce two photons. This has nothing to so with the Pauili exclusion principle; it's because angular momentum, charge and lepton number are conserved.

That seems to be the dividing line between the serious college science students and the ones who are taking the class because they have to. I've done the same thing, and just said "If you can't remember it, the derivation is trivial" and watch 90% of the students blanch in horror at the thought.

Where does QM say an electron and a photon are interchangeable?

No. Fermi particles have half-integral spin. These are the particles that obey the Pauli exclusion principle. The spin can be 1/2, 3/2, etc. You can have nuclei, atoms, or individual subatomic particles ( like electrons, neutrons and protons - all are spin 1/2). Nuclei with an odd number of nucleons (spin-1/2) will have half-integral spin. But depending on the structure, you can get larger values - Cs-133, for example, has nuclear spin 7/2. You also have Bosons, which have integral spin. 0, 1, 2... Mesons are spin 0. Nuclei with an even number of nucleons will have integral spin. Rb-87 has 87 nucleons, and the nucleus has spin 3/2. But the atom itself, because it has 37 electrons (i.e. an odd number), has an integral spin. You can't choose the spin of the atom. You can only choose the orientation (i.e. the direction the angular momentum vector points)

1 s = 2.998 X 108m only holds for light, and there is an implicit "c" in there. The correct relationship is c*(1 s) = 2.998 X 108m You don't get to arbitrarily drop units and then do unit analysis.

The derivation I gave is from the idea that work changes kinetic energy. So I imagine that the idea came from work and energy. I think that the equation became "widely used" almost immediately. It's not like physicists would have labored for years using just one or two kinematics equations, and had to wait for the others to be "discovered." All of the kinematics equations stem from the definitions of the terms and some simple calculus and algebra. They were probably all originally derived at about the same time.

Well, you'll get this thread at some point in the future, once Google has crawled it.

There is more than one way to arrive at the result. W= KE2 - KE1 for a system without potential energy. For a constant force (acceleration), W=Fs=mas=1/2mv22 - 1/2mv12 m drops out. Multiply through by 2. No time terms at all to have worried about.

Ergs, Joules, Btu, calories, electron-Volts. Doesn't matter, as long as you've done the conversion properly. They're all energy units. But yes, a g-cm2/s2 is an erg.

But that wasn't really my point. You move to the middle to capture that fraction that are on your side of the middle. If you're conservative/liberal, you don't gain extra voters by becoming more so, you gain them by moderating a little.

Bah. Trebuchets.

Exactly. If you are going slow, i.e. geologically, you might use cm/year. If you are going fast, terrestrially, you can use Mach numer. If you are going fast, relativistically, you use fractions of c. If you are going FTL, you can make up your units, because it's sci-fi.